feat(rum): scope latest-metrics RUM to locale path prefix

[alinarublea]

Why

Locale-specific sites (e.g. https://example.com/de) have no RUM domain key of their own — domain keys exist only for the main domain. Today wwwUrlResolver strips the path and the totalMetrics query aggregates RUM for the entire parent domain, so a locale site's latest-metrics reports domain-wide numbers rather than its own subtree.

What

Result-level path scoping for totalMetrics, opt-in via a new pathPrefix option:

• spacecat-shared-utils — new getBaseURLPathPrefix(baseURL) helper: extracts the locale path (https://example.com/de → /de), returns null at the domain root or for unparseable input.
• spacecat-shared-rum-api-client — the totalMetrics handler now reads opts.pathPrefix and filters bundles to that subtree before aggregating. Matching is boundary-safe: /de matches /de and /de/... but not /design.

With no pathPrefix, behavior is byte-for-byte identical to today — no existing caller is affected.

How it fits together

domain stays the bare hostname (required by the bundler URL and for domain-key resolution on the main domain). The locale scoping happens purely at the result level. The consuming side — spacecat-api-service's getLatestSiteMetrics extracting the prefix from site.getBaseURL() and passing it through — lands in a follow-up PR in that repo (this shared release must publish first).

The prefix-matching logic is intentionally kept self-contained in rum-api-client rather than importing the new util, to avoid a cross-package version bump (rum-api-client pins an exact spacecat-shared-utils version).

Out of scope

Subdomain-based locales (de.example.com) — wwwUrlResolver returns the full subdomain host, a separate case to be addressed independently.

Tests

• getBaseURLPathPrefix: root → null, trailing slash, single/multi-segment, schema-less, unparseable, null/undefined. url-helpers.js at 100% coverage.
• totalMetrics: aggregates all without pathPrefix (regression guard); scopes to subtree with it; rejects look-alike sibling paths; drops bundles with missing/invalid URLs.
• Both package suites green; coverage gates pass.

🤖 Generated with Claude Code

[MysticatBot]

Hey @alinarublea,

⚠ Degraded review - no spec document was found for this change (searched the PR links, the touched repos' docs, the architecture/guidelines docs, and linked Jira). This review covers code-level quality but could not validate the change against an agreed design, so confidence is reduced. Add a spec link (PR template section 4) and re-request review for a full-confidence pass.

Verdict: Approve - clean, well-scoped feature with solid test coverage.
Complexity: LOW - small diff, single package surface.
Changes: Adds opt-in locale path-prefix filtering to the totalMetrics RUM handler plus a getBaseURLPathPrefix utility for extracting the path prefix from a site's baseURL (6 files).

Non-blocking (3): minor issues and suggestions

• nit: matchesPathPrefix does not normalize prefix - if a caller passes /de/ (trailing slash), the boundary check path.startsWith('/de//') silently fails to match nested paths. A defensive prefix.replace(/\/+$/, '') would make this robust against future callers that skip normalization - packages/spacecat-shared-rum-api-client/src/functions/total-metrics.js:22
• nit: Silent catch blocks in both matchesPathPrefix and getBaseURLPathPrefix provide no observability signal when bundles or URLs are dropped due to parse failure. For a data-aggregation pipeline, systematically malformed URLs would silently degrade metrics with no alert - packages/spacecat-shared-rum-api-client/src/functions/total-metrics.js:23
• suggestion: Add a test for empty-string pathPrefix to lock in the falsy-means-no-filter contract, since '' could arrive from upstream coercion of a null return - packages/spacecat-shared-rum-api-client/test/total-metrics.test.js:79

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This PR will trigger a minor release when merged.